Multistage turbocompressor with diagonal-flow impellers

Abstract

The majority of the impellers of a multistage turbocompressor are diagonal-flow or "mixed-flow" type impellers with exit flow angles which are increased from the initial stage impellers toward the final stage impellers, whereby the specific speed of each impeller falls with the optimal range for that impeller.

What I claim is: 
     
       1. In a multistage turbocompressor which has a casing having suction and discharge ends, a rotating shaft passing through the casing, and a plurality of impellers fixedly mounted on the shaft in successive tandem arrangement, and which operates to draw a gas in through the suction end, to compress the gas, and to discharge the gas out through the discharge end, the improvement wherein at least some of the impellers are diagonal-flow impellers with exit flow angles less than 90 degrees, and, when the impellers are considered to be divided in a plurality of successively tandem groups each having at least one impeller, the exit flow angle of an impeller of any group nearer the suction end is made less than the exit flow angle of an impeller of a group more remote from the suction end than the first named group thereby to cause the specific speed of each impeller to be of optimal value, the exit flow angle of an impeller being the angle between the velocity component along a streamline within an imaginary meridional plane extending from the flow entrance to the flow exit of that impeller and passing through the axis of rotation thereof and the axis of rotation. 
     
     
       2. The improvement in a multistage turbocompressor as set forth in claim 1 wherein the impellers have the same outer diameter. 
     
     
       3. The improvement in a multistage turbocompressor as set forth in claim 1 or 2 wherein each of said groups has a plurality of impellers having the same exit flow angle. 
     
     
       4. The improvement in a multistage turbocompressor as set forth in claim 1 wherein the impellers have blades of blade widths which are varied among the impellers thereby to cause, in concert with the differences in the exit flow angles, the specific speed of each impeller to be of optimal value. 
     
     
       5. The improvement in a multistage turbocompressor as set forth in claim 1 wherein the exit flow angles of the impellers are within the range of 20 to 90 degrees. 
     
     
       6. The improvement in a multistage turbocompressor as set forth in claim 2 wherein the exit flow angles of the impellers are within the range of 20 to 90 degrees. 
     
     
       7. The improvement in a multistage turbocompressor as set forth in claim 3 wherein the exit flow angles of the impellers are within the range of 20 to 90 degrees. 
     
     
       8. The improvement in a multistage turbocompressor as set forth in claim 4 wherein the exit flow angles of the impellers are within the range of 20 to 90 degrees.